Dual origins of social parasitism in North American Dialictus (Hymenoptera: Halictidae) confirmed using a phylogenetic approach

The bee subgenus Dialictus (Halictidae: Lasioglossum) displays a large array of behaviours including solitary behaviour, eusociality, and social parasitism. Socially parasitic Dialictus share a suite of morphological traits; these could result from shared ancestry, but given their functional significance, could also have resulted from adaptive convergence. A combined morphological and molecular phylogenetic approach was used to test for monophyly of North American socially parasitic Dialictus. Two data sets were used in the phylogenetic analyses. First, short mitochondrial DNA sequences from previous taxonomic studies of North American Dialictus, including six social parasites, were used because of the broad taxon sampling they provide. These data were analysed in combination with a set of 40 morphological characters, including a large proportion of characters associated with social parasitism. Phylogenetic analysis of the combined DNA barcode and morphology data set resolves two distinct lineages of social parasite. The second data set was based on three genes (cytochrome c oxidase subunit 1, elongation factor 1a, and long-wavelength rhodopsin), but with sparser taxon sampling, including one representative from each putative social parasite-lineage. This also supported dual origins of social parasitism among North American Dialictus. The evolution of social parasitism is discussed.